Outage gauges (also called “fixed liquid level gauges,” or “spitter valves”) are required to be used to determine when an LP Gas tank is legally full, that is, when the liquid reaches 80% full of the maximum capacity volume. When LP Gas tanks are filled, LP Gas is released through outage gauges as a gas, as a liquid, and as a mixture of the two phases. A signal to terminate the LP Gas tank filling process occurs when liquid appears through the outage gauge. The outage gauge includes a small-bore valve located on the outside of the tank, typically on the top surface of the tank that is attached to a hollow tube which passes through the tank wall to the 80% liquid full level thereof at 40° F. It also includes a flow limiting restriction with a diameter of 0.055 in. that is typically located inside the tube.
In use, the small-bore valve is opened before the fueling process begins, and is closed at the termination of the process. A refueling operator must wear gloves to avoid burns when closing the valve. A small amount of liquid may be released when the valve is first opened, followed principally by vapor, and then mostly by liquid, when the tank has reached 80% full of maximum capacity, as the liquid enters the bottom of the outage gauge tube.
Recently, a change in air quality management rules has required that outage gauges reduce flow limiting restrictions, from the current diameter of 0.055 in. to a diameter of 0.025 in., to limit the quantity of escaping emissions (South Coast Air Quality Management District Rule #1177). To comply with this ruling, LP Gas distribution companies are required to change the outage gauges on all stationary tanks, a requirement that may necessitate the emptying of all tanks in advance of the installation of the new outage gauges. Such refitting would cost significant time and money.